1. Field of the Invention
The present invention relates to a run-flat tire improved in run-flat performance.
2. Description of the Prior Art
There are known run-flat tires capable of performing running for a relatively long distance even when the tire have been deflated due to a puncture or other factors. General run-flat tires are provided with sidewall reinforcing rubber layers at sidewall portions thereof that are formed of hard rubber for supporting load in the presence of a puncture.
FIG. 5 shows a sectional view of a conventional run-flat tire. A pair of sidewall reinforcing rubber layers “a” each have a substantially crescent shaped section and are disposed axially inside of the carcass b in the sidewall portion. Each sidewall reinforcing layer “a” includes an radially inner end p2 and an radially outer end p1.
However, a run-flat tire of such a structure is disadvantaged in that positions of the outer end p1 and the inner end p2 of the sidewall reinforcing rubber layers “a” are apt to vary widely when forming a green tire. For instance, when a part of the outer end p1 is located further inside than a tread grounding end Te in the tire axial direction, inputs from the road surface largely change within a single rotation of the tire. Accordingly, radial force variations (hereinafter referred to as “RFV”) are worsened to thereby degrade uniformity of the tire. Further, in the presence of variations in positions of the inner end p2 of the sidewall reinforcing rubber layers “a”, the longitudinal spring coefficient and the load supporting performance of the tire will be changed to lead to worsening of the RFV and worsening of run-flat performances.